Automatic fraction collector

ABSTRACT

An apparatus and method for collecting fractions from a gassegmented fluid stream including introducing a series of fluid segments into a tubular conduit and sealing the tubular conduit at either end of each injected fluid segment to form a series of individual tubular compartments with each compartment containing a single fluid segment.

United States Patent [1 1 Carleton et al.

[ 1 3,708,948 Jan. 9, 1973 [54] AUTOMATIC FRACTION COLLECTOR [75] Inventors: Joseph G. Carleton; Cassius R. McEwen; Frederick G. Williams, Jr., all of Palo Alto, Calif.

[73] Assignee: Beckman Instruments, Inc. by said Carleton and McEwen 22 Filed: Jan.11, 1971 211 Appl.No.: 105,4l7

s2 U.S.Cl ..53/74,53/266 51 lnt.Cl. ..B65b5/l0,B65b 57/12 [58] Field of Search ..53/37, 28, 74, 180, 64, 75; i4l/I0,IOL,105

[56] References Cited UNITED STATES PATENTS 3,333,391 8/1967 Horeth et al. ..53/28 Scholle ..53/28 3,397,505 8/1968 Critchell ..53/74 FOREIGN PATENTS OR APPLICATIONS 1,036,154 8/1958 Germany ..53/28 Primary Examiner-Robert C. Riordon Assistant ExaminerEugene F. Desmond Attorney-F. L. Mehlhoff and R. J. Steinmeyer [57] ABSTRACT An apparatus and method for collecting fractions from a gas-segmented fluid stream including introducing a series of fluid segments into a tubular conduit and sealing the tubular conduit at either end of each injected fluid segment to form a series of individual tubular compartments with each compartment containing a single fluid segment.

6 Claims, 12 Drawing Figures PAIENTEDJIII 9 I975 v 3. 708, 948 SHEET 1 OF 4 l5 O l2 XI SEQUENCE CONTROL UNIT I ORIvE MECHANISfl l6 r I? V /I8 MONITORING INJECTION CLAMPINC sTATION STATION sTATION FIG. I

INVENTORS 5 JOSEPH GREELEY CARLETON A cAssIus RICHARD MCEWEN FIG. 5 FIG 4 FREDERICK GARDNER WILLIAM JR.

' BY 2544M ATTORN PATENTEDJAH 9191s 8.708.948

SHEEI 2 0F 4 FIG. 7

I NVEN'TORS JOSEPH GREELEY CARLETON CASSIUS RICHARD MCEWEN FREDERICK GARDNER WILLIAMS JR.

PATENTEDJAN 9 ms SHEET 3 BF 4 INVENTCRS JOSEPH GREELEY CARLETON CASSIUS RICHARD McEWEN FREDERICK G ARQNER WLLIAMS JR.

TTORNE AUTOMATIC FRACTION COLLECTOR BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates in general to fluid material sampling apparatus and more particularly to method and apparatus for automatically collecting small sample fractions from a gas-segmented stream of fluid, such as a liquid.

2. Description of the Prior Art In many biological and chemical analyses successive fluid aliquots are dispensed into a suitable container, such as a test tube, and then subjected to an extensive examination. Typically these fluid aliquots are collected by so-called fraction collectors." Generally speaking, fraction collectors are used to successively deliver a premeasured amount of fluid sample into each of a series of test tubes disposed in a predetermined array whereby an analysis of either the collected sample itself or the collection pattern may be obtained. At

present, fraction collectors take the form of a circular array of concentric rows or a generally rectangular array of rows and columns of test tubes which array is movable relative to a suitable liquid sample dispensing head. Typical examples of commercially available fraction collectors may be found in U.S. Pat. No. 3,168,124 issued Feb. 2, 1965 under the name of-A. Lenkey and U.S. Pat. No. 3,205,925 issued Sept. 14, 1965 to Packard et al.

While some fraction collectors move the array of test tubes relative to a stationary dispensing head, others translate the dispensing. head in a predetermined fashion relative to the stationary array of test tubes and dispense or deposit a fluid sample of predetermined quantity'in each test tube contained in the array. The amount of fluid delivered to each tube is generally governed byone of three methods, namely, counting of discrete drops, dispensing the fluid for a predetermined measured time period, or accumulating and then discharging into the tube a v predetermined fluid volume.

Despite the availability of elaborate dispensing heads, a major limitation in present fraction collectors lies in their inability to deal with volumetric quantities below around-one milliliter. Although, in many applications it is unnecessary to segregate the fluid sample into fractions of less than milliliter volumetricquantities, it is becoming increasingly important in many new analytical techniques to collect and examine fluid quantities well below such a limit. For instance, fractionating a sample on the basis of the respective buoyant densities and rates of sedimentation of its con-' stituents is typically carried out by placing the sample in a receptacle containing a liquid density gradient,

wherein the density of the liquid progressively in-.

creases from the top to the bottom of the receptacle. The receptacle is then placed in a centrifuge and the sample is subjected to centrifugation to separate the sample into its various fractions. At equilibrium the sample fractions are suspended throughout the liquid at locations where the density of the fraction corresponds to that of the liquid density. Typically these fractions form very narrow bands, each of which has a volume in the microliter range. Since present fraction collectors are incapable of separating and collecting fractions of microliter quantities, any attempt to collect such small fractions in known fraction collectors only results in the remixing of the individual fractions.

Still another major drawback of present fraction collectors lies in their rather large size; despite the fact i that presently available fraction collectors are, relatively speaking, somewhat compact in size, e.g., a rectangular array of test tubes is generally around 26 inches X 17 inches X 13 inches high, they are still space-consum ing and somewhat difficult to transport from one location to another.

Furthermore, since, as previously noted, present fraction collectors consist of a geometrical array of test tubes, generally glass or plastic, each of which is open to theatmosphere, any fractions contained therein are subject to evaporation unless special design precautions are taken. Conversely, each compartment making up the fraction collector of the present invention is completely sealed off from the atmosphere thereby ensuring that collected fractions are not subject to evaporation.

SUMMARY The present invention contemplates an automatic fraction collector which not only can collect a greater number of fractions than heretofore possible, but is also capable of dispensing and storing fluid fraction volumes in the microliter range. Moreover, the fraction container itself is compact, light-weight, unbreakable and easily transportable. To this end, in accordance with the principles of the present invention, the container for the individual fractions takes the form of a long, thin-wall tubular conduit, generally formed of a suitable plastic, such as polyethylene or polyvinylchloride. A

To load the fraction collector a series of fluid segments is injected into the tubular conduit by means of a needle arrangement which is connected to a gas-segmented fluid stream containing the fractions to be collected. The tubular conduit is'sealed to form a series of tubular compartments each of which contains an individualfluid segment.

Accordingly, a primary object of the present invention is the provision of a novel automatic fraction collector.

A further object of the present invention is a fraction container able to collect greater numbers of fractions than heretofore possible.

A further object of the present invention is the provi sion of a fraction container which is compact, light weight, and unbreakable.

A further object is the provision of an automatic fraction collector which is capable of storing fluid fraction volumes in the microliter range.

Another object is a fraction container which seals the stored fluid segments from the outside environment and wherein the stored segments are not susceptible to evaporation.

Still a further object is the provision of an automatic fraction collector wherein each stored fluid segment may be easily identified for future analysis.

These and other objects and advantages of the invention will become apparent from the following detailed description read in conjunction with the accompanying drawings in which:

DETAILED DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic view in block form illustrating the general arrangement of the automatic fraction collector in accordance with the principles of the present invention;

FIG. 2 is a diagrammatic view showing the details of the. monitoring station; h

7 FIG .'3 is a cross-sectional view of the apparatus comprising the injection station;

FIG. 4 is a crosssection of the tubular conduit at the injection station showing the position of the needle inside the tubular conduit as liquid is being injected therein;

FIG. Sis a cross-section taken along the line 5 -5 of FIG. 4 showing in detail the position of the needle lumen inside the tubular conduit;

FIG. 6 is a. partially exploded perspective view of the clamping station;

FIG. 7 is a front view of the generally circular disc and pin combination illustrated in FIG. 6;

FIG. 8 is a partially exploded view showing the details of the clamping armsand the fixed plate;

FIG. 9 is a diagrammatic view of the clamping arm illustrating the means for tightly holdingthe heater element;

FIG. 10 is a schematic wiring diagram of the sequence control unit;

FIG. 11 is a diagrammatic view of the tubular conduit fraction container illustrating the series of tubular compartments each of which holds a liquid segment;

FIG. 12 is a diagrammatic view of the liquid segments being injected and sealed within the tubular conduit. a

With reference now to the drawings,'and moreparticularly to FIG. 1 thereof, it will be observed that the reference numeral 10 designates. a thin-wall tubular conduit which is driven from left to right in the direction of the dotted arrow between a supply reel 11 liquid segments by a suitable gas slug (such as an airslug). A conventional means for dividing a liquid stream into a series of successive liquid segments separated from each other by intervening air-slugsior segments is shown in U.S. Pat. No. 2,797,149.

The monitoring station 16 senses the presence of a liquid segmentintroduced into the tube by injection station-1 7 and provides an electrical signal which is fed to a sequence control unit 15. The sequence of functionaI operations performed by monitoring station 16, injection station 17, clamping station 18, and drive mechanism 19, is governed by sequence control unit in a manner to be presently described.

DRIVE MECHANISM As previously noted, drive mechanism 19 functions to advance tubular conduit 10 in a stepwise fashion past injection station 17 so that successive fluid aliquots may be stored in the conduit. Preferably, each drive step advances conduit 10 an equal and predeterother side of and in contact with tubular conduit 10 to anda take-up reel 12 by means of a friction-drive capstan l3 and idler wheel 14. The supply reel 11 rotates freely on a fixedspindle while the take-up reel 12 is driven by a suitable motor (not shown) which motor is torque-limited to about 1 inch-lb. to limitthe tensile force imparted to the tubular conduit so that the conduit is not inadvertently broken. Tubular conduit 10 may be fabricated from a suitable transparent or translucent plastic material, such as polyethylene orpolyvinylchloride, and typically has an outside diameterof around l/l6inch to. ,5 inch. Of course, it will beappreciat'ed that the foregoing conduit dimensions are merely exemplary and other size conduits may be used.

Tubular conduit 10 is driven in a step-wise fashion sequentially past a monitoring station 16, an injection station 17, and a clamping station 18, by the combination of drive mechanism l9'and friction drive capstan l3 and idler wheel 14. A small liquid segment or aliquot is introduced into the tubular conduit as it passesby the injection station 17. The clamping station 18 serves to seal the tubular conduit at either end of each liquid segment to form a series of compartments, each of which containsa individual liquid segment.

The liquid segments are fed to the injection station 17 in the form of a gas-segmented liquid stream. That is, each liquid. segment is separated from adjacent maintain the tubing in frictional engagement with drive wheel 13. In this context it should be noted that the tubular conduit 10 is wrapped approximately'half-way aroundthe drive wheel 13 to provide a large contact area so that a substantial friction force is capable of driving conduit 10 while requiring only a small spring force on the idler wheel.

By way of example, the drive mechanism 19 ad- .vances the tubular conduit about I 54; inch per electrical impulse. The time required to advance thetubular conduit this predetermined distance is about one-half second while another 2 seconds'is required for the Geneva mechanism to continue to rotate around to the initial position where it will again be ready to advance the tubular conduit 10. v

I INJECTION STATION A series of liquid segments or aliquots separated by gas-slugs, such asair-siugs, is introduced or-injected into the tubular conduit 10 as it is driven in' a step-wise fashion past injection station 17. As; may be readily seen from an inspection of FIG. 3, th'e liquid segments are successively introduced into the tubularconduit 10 by means of a thin needle'20, one end of which is connected to a connecting conduit 21 through which the liquid sample stream is transmitted to the fraction collector. The gas-segmented liquid stream -is forced through the connecting conduit 21 and needle 20 by a suitable pump (not shown) whose'operation may be selectively controlled. The needle 20 is inserted through a circular bore provided in a needle holder 22, typically formed of a small plastic block, and tightly held within the bore by means of a knurled thumbscrew 24.1'Ihe bottom end'of needle 20 extends downwardly through a narrow bore 23 formed'in a needle guide block 25 whichguide'block takes the same general shape as needle holder 22. Immediately below the needle guide block 25, there is provided a stop block 26, including a longitudinal slot 27 located directly beneath needle 20 and through which the tubular conduit travels. The height and width of guide slot 27 is equal to that of the diameter of tubular conduit 10 so that it adequately supports the conduit and prevents it from collapsing when needle isinserted.

A drive shaft 28 is movably retained within an aperture provided in needle guide block by means of a bushing 29 and is connected to needle holder 22 by insetting one end of the shaft 28 inside an internally threaded bore provided in needle holder 22. Drive shaft 28 is vertically driven in an up and down direction by means of Ledex rotary solenoid 30 which is connected to drive shaft 28 by a pivot arm and rotary link arrangement 31. Upon actuation of rotary solenoid 30 pivot arm 28 rotates in a somewhat elliptical path in a counter-clockwise direction which in turn pulls drive shaft'downward in a vertical direction to thereby insert needle 20 through the tubular conduit-l0. When the rotary solenoid 30 is de-energized, a return spring (not shown) causes pivot arm 28 to rotate back 'in a clockwise direction pushing drive shaft 28 vertically upward to thereby withdraw needle 20. The drive shaft includes a pair of adjustable lock nuts 32 and 33 interposed between needle holder 22 and guide block 25, whose position may be selectively adjusted to vary the extend of downward travel of needle 20. In this manner the vertical travel of .drive shaft 28 may be set so that needle 20' pierces the top wall of the tubular conduit, but does not reach the bottom wall.

As best shown in FIGS. 4 and 5, the end 35 of needle 20 is ground at an oblique angle, around with respect to the needle axis to ensure that the needle lumen (opening) 36 is entirely enclosed within the tubular conduit 10 while the liquid segments are being injected therein to prevent inadvertent leakage. It has been found that by fabricating the needle in this manner, the outer wall of the tubular conduit seals around the puncture point so effectively that a pressure on the order of 15 p.s.i. may be contained without danger of leadage. The needle lumen 36 is orientated so that the liquid segments are directed to the left toward the monitoring station, as shown in FIG. 4 as they areinserted inside tubular conduit 10.

MONITORING STATION Monitoring station 16 is located a predetermined distance downstream from injection station 17 to sense the presence or absence of a liquid segment in the tubular conduit 10. Typically, monitoring station 16 comprises a source of light 40 located on one side of tubular conduit 10 and a suitable photocell 41, such as a phototransistor, disposed on the opposite side of the tubular conduit 10 diametrically opposite to the source of light 40. Both light source 40 and photocell 41 are enclosed within a light tight housing 42. In the absence of a liquid segment in the tubular conduit, the beam of light radiated by light source 40 is scattered by the walls of tubular conduit 10 and, hence, the intensity of the light beam passing through the conduit falls below that required to actuate photocell 41. As a result the absence of a liquid segment is manifested by the off" condition of photocell 41. Conversely, a liquid segment in the conduit serves as a lens and focuses the light '6 a beam onto the photocell 4.1 switching the photocell to its on condition. Thus, photocell 41 provides an electrical signal upon the occurrence of a liquid segment in tubular conduit 10. This signal is coupled to sequence control unit 15, which in turn de-energ'izes solenoid 30 in a manner to be presently described to withdraw injection needle 20 from the tubular conduit 10.

CLAMPING STATION Once a liquid segment is injected into tubular conduit 10, the conduit is sealed at either end of the liquid segment to form an air-tight compartment which. en-

closes the individual liquid segment. This encapsulating function is carriedout by the clamping station 18, the details of which are illustrated in FIGS. 6 through 9. As diagrammatically illustrated in FIG. 12 successive liquid segments (L) separated by gas slugs (G) are transmitted through connecting conduit 21 and needle 20 as a gas-segmented liquid stream. The, gas segmented stream is then injected in to conduit 10 (traveling from left to right) with the conduit 10 being sealed at either end of each liquid segment 10l-(at clamping station 18) to form the air-tight compartment which stores the individual liquid segment.

Generally speaking, the clamping station comprises two movable, heated jaws, which are pressed together by a motor driven cam arrangement around the outside of the tubular conduit to heat-seal the tubing at either end of an injected liquid segment over the puncture caused by the injection needle. Each jaw includes an Ungar heating unit 43 (soldering gunheater) having a stainless steel tip 44 secured to one end thereof. The heating surface 45 of each stainless steel tip 44 includes a narrow protruding ridge 46 along the top edge thereof. These narrow ridges 46 cooperate with each' other as the heating jaws are pressed together to prevent excessive squeezing of the tubular conduit. The Ungar heating unit 43 is connected by way of a suitable socket 47 me suitable source of control voltage (not shown) which may be varied to selectively adjust the temperature of the sealing jaws. v

Each heating jaw is held inside a U-shaped supporting member 48 by placing a similarly shaped member 49 over the heating unit 43 and tightly connecting it to the U-shaped holding member 48 by a pair'of suitable threaded bolts 50 and 51. i

To prevent inadvertent damage to the tubular conduit as the jaws seal the conduit at either end of a liquid segment, it is desirable that the jaws are smoothly pressed together around the tubular conduit. To this end, as best illustrated in FIG. 8, each U-shap'ed holding member is pivotally coupled to one of the lower corners of a generally rectangular stationary plate 52 by means of a pivot pin 53. Stationary plate 52 includes a pair of arcuate shaped slots 54 on either side thereof and a guide recess 55 (FIG. 6) in which a narrow ridge 56 of a movable plate 57 is slidably retained. Movable plate 57 also includes a pair of similarly shaped arcuate slots 58 overlying, generally, the arcuate slots 54 formed in the stationary plate 52. A small drive pin 59 protrudes from one side off each holding member 48 and projects through communicating arcuate slots 54 and 58.

On the front surface of movable plate 57 there is provided a narrow flange element 60 having a laterally curved surface 61 which serves as a cam surface. Cam surface 61 cooperates with a pin element 62 protruding from an adjustable actuating member 69 which in turn is secured to the face of a supporting circular disc 63 mounted at one end of a rotatable shaft 64. Rotatable shaft 64 is driven in a clockwise direction by motor 65 I which is operatively connected to the rotatable shaft 64 by way of a suitable gear train 66. v

A norm ally closed microswitch 67 is located immediately below circular disc 63 with its armature 68 lying in the path of travel of an actuatingrnember 69,

also, carried by circular disc 63. Microswitch 67 is connected in circuit (in a manner to be presently discussed) with an electromagnetic relay which serves to actuate motor 65. Thus, as circular disc '63 rotates actuating member 69 engages armature 68 once each revolution of disc 63 to thereby interrupt the current supplied to motor 65and terminate the. rotation'of disc.

As previously noted, pin 62 rides along the cam surface 60 of flange. 61 projecting from an inwardly as+ heating units 43 dwell in a fixed closed position for about one-fifth. of a'revolution. Obviously, the time of dwell may be easily varied by merely adjusting the distance R and the axis of rotation of shaft 64 with respect to cam surface 60 so thatpin member 62 contacts cam surface .60 a shorter or longer time during each revolution of disc 63.

While it is not specifically illustrated in many in- SEQUENCE CONTROL UNIT As shown in FIG. 10, the sequence control unit .10 consists, generally speaking, of a number .of multi-armature electromagnetic relays functionally interconnected-to actuate the drive mechanism 19, injection station '17, and clamping station l8 in the proper sequence and for the requisitetimc intervals. Each armature serves as a single pole-double throw switch to interconnect or disconnect an associated input line with an output line. For convenience and in the interest of clarity the armatures of each relay have been designated a, b, c, etc. with the lowermost armature bearing thetirst letter a and the succeeding armatures being designated b,=etc.

Power is supplied to the driving mechanism 19 from v a suitable power supply (not shown), such as 24 voltsstances it may be desirable to position a suitable air blower downstream from the clampingstation 18. In this manner immediately after the tubular conduit has been squeezedand sealed by heating-it may be subjected to a momentary air blast to cool the tubular conduit and accelerate its tensile strength recovery thereby minimizing any danger of cracking or breakage.

While for purposesof description'a heat-sealing type of clamping device has been described, it will be understood that other forms of clamping mechanisms may be utilizedin the present invention. For instance, each fraction compartment may be sealed ateither end by an external. metal clamp. In, this case the clamping device would, perhaps, use a supply reel of a metal strip in combination with a cut-off and clamping die which would both cut off the required length of the metal and tightly clamp the tubing shut. That is, in principle much like commercially available continuous-wire paper staplers. 'Or, in the alternative, at least in many instances, no clamping whatsoever would be required. That is to say, if the injection needle was sufiiciently small in diameter the injected fractions-would remain ina fixedposition in the tubing even without-a clamp and the punctured hole would be essentially self seald.c., via normally closed microswitch 85, bus 81,'line 82, relay 77 armature c, line 83, line 84, and relay 29 armature a. The sample injector receives its power via lines 86, 87, relay 76 armature b, lines 88, full wave rectifier 91, line 89 and line 90 while power is fed to the clamping station by way of relay 76 armature b, line 88, line 93, relay'80 armature b, and lines 94 and 89. The microswitch 68 is located in series with relay 80 and connected to output line 88 via connecting line 92.

As previously noted when normally open microswitch 67 is actuated by member 69 once during each revolution of circular disc 63, armature 68 closes therebyclosing relay 80 and opening armature b to interrupt the power to the clamping station and release the clamping jaws. Microswitch 68 is closed momentarily, however, relay 80 remains closed via the circuit over line 92 and armature a which is now connected to the lower contact. Relay 80 returns to its open position when relay 76 is open.

OPERATION To facilitate a complete understanding of the present invention perhaps it would be best to discuss briefly one complete cycle of operation. For purposes of discussion it will beassumed that each of the relays through initially reside in its -open position wherein the'armatures rest in their upward position as illustratedin the circuit diagram of FIG. 10.

To initiate the operation, the operator pushes button 95 which closes relay 77 via lines 86 and 94. Once closed relay 77 is held in its closed'position by current supplied through normally open microswitch 85, line 81,-line 96 and armature a. The closing of relay 77 completes the current path to relay, 79 over lines 81, 82, armature c relay 77, line 83, and line 84..This drive mechanism 19 is thus turned on and stepstubular conduit 10 one increment. After the tubular conduit-10 Shortly thereafter microswitch 67 is momentarily closed closing relay 80 and breaking the circuit to the clamping station thereby releasing the clamping jaws. Monitoring station 16 then senses the liquid segment being injected into tubular conduit and provides an electrical signal to relay 78 closing this relay. The closing of relay 78 opens relay 76 thereby breaking the circuit to the sample injector and causing the needle injector to withdraw from tubular conduit 10. More specifically, relay 76 is opened since armature b relay 78 is disconnected from connecting line 98. The opening of relay 76 also ensures that clamping station remains de-energized even through relay 80 has returned to its normally open position since microswitch 68 returns to its open position shortly after being closed by actuating arm 69.

The closing of relay 78 also again energizes drive mechanism 19 by way of line 81, armature d relay 78, line 100, line 84, and armature a relay 79. Once energized the driving mechanism 19 again steps tubular conduit 10 another selected increment wherein it is ready for the injection of a successive liquid sample. Of course, once the tubular conduit 10 is stepped relay 78 returns to its normally open position since theelectrical signal for monitoring station 16 ceases. At this stage the control circuit is again ready for a new cycle.

TUBULAR CONDUIT FRACTION CONTAINER FIG. 11 illustrates the fraction container after a number of successive samples have been injected into the tubular conduit 10 in accordance with the principles of the present invention. As can be seen the end fraction container consists of a plurality of successive compartments 100 formed along'the body of tubular conduit 10 each compartment of which contains an individual liquid segment. If desired, a suitable stamping device may be provided for labeling the compartments for future use.

As will be readily appreciated, the number of fractions collected is limited only by the length of the tubular conduit 10 used. Moreover, the fraction container itself is fleiiible' enabling it to be rolled up and stored in a relatively small space.

Numerous modifications and departures from the specific apparatus described herein may be made by those skilled in the art without departing from the inventive concept of the invention. Accordingly, the invention is to be construed as limited only by the spirit and scope of the appended claims.

What is claimed is: a v

1. An apparatus for collecting sample liquid fractions from a gas-segmented liquid stream in a tubular conduit comprising: means for injecting aseries of liquid segments into the tubular conduit, means located on one side of said injection means for sealing the conduit at one end of the injected liquid segment, means disposed on the other side of said injecting means and cooperating with said tubular conduit for providing an output signal upon sensing the presence of a liquid segment in the tubular conduit, means responsive to said output signal for withdrawing'said injecting means from the tubular conduit, means to advance the tubular conduit a predetermined distance, and means for actuating said sealing means to seal the tubular conduit at the other end of the liquid segment to form a series of tubular compartments each 0 which contains a small liquid segment.

2. An apparatus as defined in claim 1 wherein said injection means comprises a needle connected to a source of a gas-segmented liquid stream, means for pumping the gas-segmented liquid stream through the v needle and means for puncturing the outer wall of said tubular conduit with said needle.

3. An apparatus as defined in claim 1 wherein said sealing means comprises means for compressing together and momentarily heating the opposite walls of said tubular conduit.

4. An apparatus for collecting liquid fractions from a gas-segmented liquid stream comprising: injection means disposed adjacent to a tubular conduit for injecting a series of liquid segments into the tubular conduit, sealing means disposed upstream a predetermined distance from said injection means for sealing the conduit at one end of each injected liquid segment, control means connected to both said injection means and said sealing means, said control means simultaneously actuating said injection means and said sealing means, sensing means disposed downstream a predetermined distance from said injection means for providing an electrical output signal upon sensing the presence of a liquid segment in said tubular conduit, drive means for advancing said tubular conduit a predetermined distance, said control means being responsive to said electrical output signal to deactivate said injection means and actuate said drive means, said sealing means being actuated upon the termination of the tubular conduit movementto seal the conduit at the other end of each liquid segment to form a series of tubular compartments each of which containsan individual liquid segment. I

5., An apparatus for collecting liquid fractions as defined in claim 4 wherein said injection means comprises a tubular-like needle through which the liquid segments flow and means responsive to said control means for causing said needle to puncture the wall of said tubular conduit whereby a liquid segment is introduced into the tubular conduit.

6. An apparatus for collecting liquid sample fractions as defined in claim 5 wherein said sealing means comprises means for compressing and momentarily heating 

1. An apparatus for collecting sample liquid fractions from a gas-segmented liquid stream in a tubular conduit comprising: means for injecting a series of liquid segments into the tubular conduit, means located on one side of said injection means for sealing the conduit at one end of the injected liquid segment, means disposed on the other side of said injecting means and cooperating with said tubular conduit for providing an output signal upon sensing the presence of a liquid segment in the tubular conduit, means responsive to said output signal for withdrawing said injecting means from the tubular conduit, means to advance the tubular conduit a predetermined distance, and means for actuating said sealing means to seal the tubular conduit at the other end of the liquid segment to form a series of tubular compartments each of which contains a small liquid segment.
 2. An apparatus as defined in claim 1 wherein said injection means comprises a needle connected to a source of a gas-segmented liquid stream, means for pumping the gas-segmented liquid stream through the needle and means for puncturing the outer wall of said tubular conduit with said needle.
 3. An apparatus as defined in claim 1 wherein said sealing means comprises means for compressing together and momentarily heating the opposite walls of said tubular conduit.
 4. An apparatus for collecting liquid fractions from a gas-segmented liquid stream comprising: injection means disposed adjacent to a tubular conduit for injecting a series of liquid segments into the tubular conduit, sealing means disposed upstream a predetermined distance from said injection means for sealing the conduit at one end of each injected liquid segment, control means connected to both said injection means and said sealing means, said control means simultaneously actuating said injection means and said sealing means, sensing means disposed downstream a predetermined distance from said injection means for providing an electrical output signal upon sensing the presence of a liquid segment in said tubular conduit, drive means for advancing said tubular conduit a predetermined distance, said control means being responsive to said electrical output signal to deactivate said injection means and actuate said drive means, said sealing means being actuated upon the termination of the tubular conduit movement to seal the conduit at the other end of each liquiD segment to form a series of tubular compartments each of which contains an individual liquid segment.
 5. An apparatus for collecting liquid fractions as defined in claim 4 wherein said injection means comprises a tubular-like needle through which the liquid segments flow and means responsive to said control means for causing said needle to puncture the wall of said tubular conduit whereby a liquid segment is introduced into the tubular conduit.
 6. An apparatus for collecting liquid sample fractions as defined in claim 5 wherein said sealing means comprises means for compressing and momentarily heating the opposite walls of the conduit. 